Koslow

A round face and a prominent, bulbous nose give Koslow a distinctive look beneath his short dark hair. He is neither tall nor short, and in combat he outfits himself like any other Marleyan officer, helmet included.

Two traits define Koslow: professional competence and contempt. As Magath's adjutant he is observant and reliable, feeding his commander battlefield reports and tactical suggestions at every turn. Toward Eldians, however, he shows open bigotry, branding them devils and belittling the Warrior candidates who serve under him despite granting them a grudging measure of respect. His cruelty can be casual; he treats the trauma of shell-shocked Eldian veterans as a source of entertainment.

When the Marley Mid-East War reaches its final engagement at Fort Slava, Koslow fights beside Magath, scolding the candidate Colt Grice for doubting the offensive and later announcing the approach of an enemy armored train fitted with anti-Titan artillery. When Falco Grice risks himself to rescue a wounded enemy soldier, Koslow reprimands the boy, then laughs aloud as the rescued man curses his Eldian saviors in his own language. After Zeke Yeager's Titans fall on the fort, he reminds the candidates that their own ancestors once inflicted identical horrors on Marley.

Back home he escorts the Warriors into the Liberio internment zone, growing irritated on the train ride by their loud celebrating, and explains to Falco that the injured Eldians filing past are trauma cases bound for hospital treatment, a sensitivity he happily exploits for a laugh. When the Tybur family arrives unexpectedly, he carries the news to Magath. A month later he monitors Willy Tybur's festival production alongside his commander, mobilizes the reserves when the Warriors go missing, and stays at Magath's side once the Attack Titan erupts from the stage. He questions the decision to fire anti-Titan rounds while the Founding Titan hangs in the balance, but Magath explains that Marley's new doctrine no longer leans on Titan power.

In the battle's aftermath Koslow helps shield the wounded Pieck Finger, pulling her into a building with Gabi and Falco and warning the children away from the window. He fails to stop the pair when they chase after Eren, and when Magath returns he is tending Pieck's injuries, reporting that the two never came back.